Ladder-type cable trays comprise pairs of beamed or spined members having regularly spaced transverse arms between said spines for cradling cables, wiring, tubes and the like, such as for computer networks, telecommunications and the like. Ladder-type cable trays normally are suspended from ceilings on rods. In computer network installations, ladder-type cable trays are used for routing network cables along the ceiling of a dedicated room to upright components known as racks. Occasionally, the ladder-type cable trays might be laid out on top of the racks. Ladder-type cable trays are often found in large installations where they may travel great distances, both indoors and outdoors, such as at petroleum refineries and the like.
It is also necessary, however, to run electrical power into and around the area to the racks and to other related equipment served by the cable trays. For purposes of isolating the electrical power wiring from interference with communication signals in the network cables, and for reasons of safety, electrical power wiring typically is carried within the hollows of separately mounted ducts called raceways. Prior art ladder-type cable trays, which are limited to carrying externally exposed cabling, therefore are not suitable for electrical wiring. To run electrical wiring along the cable arms thereof would not be in compliance with building code requirements. In order to meet building code requirements and the IEEE specifications, a metallic barrier must separate electrical wiring and low voltage cabling.
Prior developments in this field may be generally illustrated by reference to the following information disclosure statement:
U.S. Patent Documents U.S. Pat. No. Patentee Issue Date 5,629,496 J. Navazo May 13, 1997 5,659,151 J. Dale Aug. 19, 1997 5.123,618 D. Geterman et al. Jun. 23, 1992 5,323,988 I. Handler Jun. 28, 1994 5,131,860 S. Bogiel Jul. 21, 1992 4,166,195 A. Schwab Aug. 28, 1979 4,017,137 W. Parks Apr. 12, 1977 5,614,695 J. Benito Navazo Mar. 25, 1997
U.S. Pat. Nos. 5,123,618 and 5,323,988 teach typical cable trays having arms that are designed to hold multiple strands of cable in a distribution system.
U.S. Pat. Nos. 5,131,860, 4,166,195, 4,017,137 and 5,614,695 teach electrical wiring raceways comprising hollow ducts with snap-on covers. Some of these covers feature knockout or punch-out tabs for accepting electrical outlets.
U.S. Pat. Nos. 5,629,496 and 5,659,151 teach other box-like hollow mechanisms having provisions for electrical outlets and wiring.
It is possible to find ladder-type cable trays and electrical raceways mounted side-by-side in a single installation, resulting in a great deal of duplication of effort, materials and the like--not to mention the amount of space wasted in rooms, corridors, and the like--which often are no larger than closets. There has been no suggestion in the art that such unnecessary duplication could be eliminated were a single device to be designed to perform both functions safely.
Accordingly, there continues to be a need for a new and improved ladder-type cable tray which addresses the problems of construction, effectiveness and ease of use that are attendant in the prior art. In this respect, the present invention substantially fulfills this need.